Cardiovascular disease, including atherosclerosis, is the leading cause of death in the United States. One method for treating atherosclerosis and other forms of arterial lumen narrowing is percutaneous transluminal angioplasty, commonly referred to as “angioplasty” or “PTA,” or “PTCA” when performed in the coronary arteries. The objective in angioplasty is to restore adequate blood flow through the affected artery, which may be accomplished by inflating a balloon of a balloon catheter within the narrowed lumen of the artery to dilate the vessel.
The anatomy of arteries varies widely from patient to patient. Often a patient's arteries are irregularly shaped, highly tortuous and very narrow. The tortuous configuration of the arteries may present difficulties to a clinician in advancement of the balloon catheter to a treatment site. In addition, in some instances, the extent to which the lumen is narrowed at the treatment site is so severe that the lumen is completely or nearly completely obstructed, which may be described as a total occlusion. If the occlusion has been established for a long period of time, the lesion may be referred to as a chronic total occlusion or CTO. Chronic total occlusions are often characterized by extensive plaque formation and typically include a fibrous cap surrounding softer plaque material. This fibrous cap may present a surface that is difficult to penetrate with a conventional medical guidewire such that one method of crossing a chronic total occlusion includes utilizing a stiffer guidewire to create a new channel through the occlusion.
Due to the fibrous cap of the total occlusion, a stiffer guidewire still may not be able to cross the occlusion and the distal end of the guidewire may buckle or prolapse within the vessel when force is applied. In addition, a clinician must take greater care to avoid perforation of the vessel wall when using a stiffer guidewire. Further, even if a stiffer guidewire can penetrate the proximal fibrous cap of the total occlusion, it may not be able to completely cross the occlusion due to multiple non-functional channels that often occur throughout the occlusion, which if entered by the guidewire lead to dead-end pathways and/or to the creation of false tracts within the occlusion and the problems attendant thereto.
Another challenge with the treatment of chronic total occlusions is that even after a guidewire successfully crosses the occlusion, the clinician may not be able to advance a dilatation balloon over the guidewire due to the fibrocalcific composition of the chronic total occlusion. In such situations, additional or alternative interventional devices may be needed to treat the occlusion further complicating the procedure. Accordingly, there exists a need in the art for improved devices and methods for treatment of a CTO.